st: making data duplicate in terms of several variables in case of a given variable taking identical values

[Ekaterina Hertog <ekaterina.hertog@sociology.ox.ac.uk>]

Dear all,
I have some data which looks like this
zipcode        prefecture    towncode    areacode
0010027    hokkaido    100        1100
0010029    hokkaido    100        1100
0010029    .        .        .
0010030    hokkaido    100        1100
0200822    iwate        201        3201
0200823    .        .        .
0200823    iwate        201        3201
0200831    iwate        201        3201
I use Stata 11.

I would like to make my observations identical in terms of prefecture, 
towncode and areacode when they are identical in terms of zipcode. I 
think that the only cases where prefecture, towncode and areacode vary 
while zipcodes are identical are when prefecture, towncode and areacode 
are sometimes missing and sometimes not, but I would like to check that 
before I do the necessary replacements.
I looked into duplicate commands, but did not seem to find a good 
solution. I would be most grateful for any pointers.
Sincerely yours,
katya

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